Search results for "Quasiparticle"
showing 10 items of 280 documents
GW quasiparticle energies of atoms in strong magnetic fields
2019
Quasiparticle energies of the atoms H–Ne have been computed in the GW approximation in the presence of strong magnetic fields with field strengths varying from 0 to 0.25 atomic units (0.25 B 0 =0.25 ℏe −1 a −2 0 ≈58 763 0.25 B0=0.25 ℏe−1a0−2≈58 763 T). The GW quasiparticle energies are compared with equation-of-motion ionization-potential (EOM-IP) coupled-cluster singles-and-doubles (CCSD) calculations of the first ionization energies. The best results are obtained with the evGW@PBE0 method, which agrees with the EOM-IP-CCSD model to within about 0.20 eV. Ionization potentials have been calculated for all atoms in the series, representing the first systematic study of ionization potentials …
Nuclear matrix elements for double beta decay in the QRPA approach: a critical review
2009
The calculation of nuclear matrix elements (NME) for double beta decay transitions (DBD) relies upon several approximations. The purpose of this note is to review some of these approximations, and their impact upon the NME. We shall present our results, which have been obtained in the framework of the proton-neutron quasiparticle random phase approximation (pnQRPA), and we shall focus on short range correlations, pairing, and symmetry effects.
Orbital-selective Mott Transitions in a Doped Two-band Hubbard Model
2009
We extend previous studies on orbital-selective Mott transitions in the paramagnetic state of the half-filled degenerate two-band Hubbard model to the general doped case, using a high-precision quantum Monte Carlo dynamical mean-field theory solver. For sufficiently strong interactions, orbital-selective Mott transitions as a function of total band filling are clearly visible in the band-specific fillings, quasiparticle weights, double occupancies, and spectra. The results are contrasted with those of single-band models for similar correlation strengths.
Disorder and localization effects on the local spectroscopic and infrared optical properties ofGa1−xMnxAs
2015
We study numerically the influence of disorder and localization effects on the local spectroscopic characteristics and infrared optical properties of ${\text{Ga}}_{1\ensuremath{-}x}{\text{Mn}}_{x}\text{As}$. We treat the band structure and disorder effects at an equal level by using an exact diagonalization supercell simulation method. This method accurately describes the low-doping limit and gives a clear picture of the transition to higher dopings, which captures the localization effects inaccessible to other theoretical methods commonly used. Our simulations capture the rich in-gap localized states observed in scanning tunneling microscopy studies and reproduce the observed features of t…
Decay of Neutron-Rich Mn Nuclides and Deformation of Heavy Fe Isotopes
1998
The use of chemically selective laser ionization combined with beta-delayed neutron counting at CERN/ISOLDE has permitted identification and half-life measurements for 623-ms Mn-61 up through 14-ms Mn-69. The measured half-lives are found to be significantly longer near N=40 than the values calculated with a QRPA shell model using ground-state deformations from the FRDM and ETFSI models. Gamma-ray singles and coincidence spectroscopy has been performed for Mn-64 and Mn-66 decays to levels of Fe-64 and Fe-66, revealing a significant drop in the energy of the first 2+ state in these nuclides that suggests an unanticipated increase in collectivity near N=40.
Neutral-current supernova-neutrino cross sections for Pb204,206,208 calculated by Skyrme quasiparticle random-phase approximation
2019
The present work constitutes a detailed study of neutral-current (NC) supernova-neutrino scattering off the stable even-even lead isotopes Pb204,206,208. This is a continuation of our previous work [Almosly et al., Phys. Rev. C. 94, 044614 (2016)10.1103/PhysRevC.94.044614] where we investigated charged-current processes on the same nuclei. As in the previous work, we have adopted the quasiparticle random-phase approximation (QRPA) as the theory framework and use three different Skyrme interactions to build the involved nuclear wave functions. We test the Skyrme forces by computing the location of the lowest-order isovector spin-multipole giant resonances and comparing with earlier calculati…
Turnstile behaviour of the Cooper-pair pump
2003
We have experimentally studied the behaviour of the so-called Cooper pair pump (CPP) with three Josephson junctions, in the limit of small Josephson coupling EJ < EC. These experiments show that the CPP can be operated as a traditional turnstile device yielding a gate-induced current 2ef in the direction of the bias voltage, by applying an RF-signal with frequency f to the two gates in phase, while residing at the degeneracy node of the gate plane. Accuracy of the CPP during this kind of operation was about 3% and the fundamental Landau-Zener limit was observed to lie above 20 MHz. We have also measured the current pumped through the array by rotating around the degeneracy node in the ga…
A 5E-Based Learning Workshop on Various Aspects of the Hall Effect
2019
Learning activities in constructivist environments are characterized by active engagement, inquiry, problem solving, and collaboration with peers. The 5E learning cycle is a student-centered instructional model for constructivism, where the students perform five phases of instruction: Engagement, Exploration, Explanation, Elaboration, Evaluation. The purpose of this contribution is to present a 5E-based learning path of advanced physics aimed at strengthening Physics/Engineering student understanding about the quantum Hall effect, a phenomenon observed at low temperatures in a two-dimensional electron gas subject to a strong perpendicular magnetic field. The quantum Hall effect, a rare exam…
Decays of110Rhand112Rhto the near neutron midshell isotopes110Pdand112Pd
1999
The decays ${}^{110}\mathrm{Rh}$ and ${}^{112}\mathrm{Rh}$ have been investigated using on-line mass separation with the ion-guide technique. Extended decay schemes have been constructed for both the low- and high-spin states in ${}^{112}\mathrm{Rh}$. Mixing ratios for the collective transitions from the ${2}_{2}^{+}$ and ${3}_{1}^{+}$ states in ${}^{112}\mathrm{Pd}$ have been measured by $\ensuremath{\gamma}\ensuremath{-}\ensuremath{\gamma}$ angular correlation. The presence of two sets of ${0}^{+}$ and ${2}^{+}$ states in the 1.1\char21{}1.4 MeV range suggests the existence of an intruder band, the energy of which is the lowest in ${}^{110}\mathrm{Pd}$ with two neutrons fewer than the mid…
In-source laser spectroscopy of75,77,78Cu: Direct evidence for a change in the quasiparticle energy sequence in75,77Cu and an absence of longer-lived…
2011
This paper describes measurements on the isotopes (75,77,78)Cu by the technique of in-source laser spectroscopy, at the ISOLDE facility, CERN. The role of this technique is briefly discussed in the ...